The present invention relates to a computer system and a legacy boot method for the computer system and more particularly to a computer system which can boot a legacy operating system in a computer system having no physical BIOS (Basic Input/Output System) and a legacy boot method for the computer system.
Control for an input/output (I/O) device performed by boot processing of the legacy operating system which is an old-type operating system requiring BIOS provided in a computer system is performed by calling BIOS by INT (interrupt) instruction issued by bootstrap code and executing BIOS code incorporated in ROM of physical I/O device provided in hardware. Heretofore, this control gets no further than realizing I/O operation of low level in boot processing on a monitor of virtual machine.
As a prior art relative to booting of the legacy operating system, there is known technique described in U.S. Pat. No. 7,103,529B, Zimmer, for example. This prior art relates to technique of improving security for I/O control in virtual computer and technique of emulating BIOS code of I/O device when extended firmware is used upon calling of BIOS.